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Technique for Raising H(c) in Ferromagnetic Thin Films

IP.com Disclosure Number: IPCOM000076356D
Original Publication Date: 1972-Feb-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Lee, K: AUTHOR

Abstract

An important property of continuous ferromagnetic films for magnetic recording is the coercive field H . It is known that the size of the magnetic transition, or the size of the "bit," is inversely proportional to H(c). Discussed is a technique for raising H(c) in a ferromagnetic film. Also, the rate of change of H(c) with increasing temperature (T) is increased.

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Technique for Raising H(c) in Ferromagnetic Thin Films

An important property of continuous ferromagnetic films for magnetic recording is the coercive field H . It is known that the size of the magnetic transition, or the size of the "bit," is inversely proportional to H(c). Discussed is a technique for raising H(c) in a ferromagnetic film. Also, the rate of change of H(c) with increasing temperature (T) is increased.

This technique is based on the strain inherent in an homogeneous film. By periodically varying the composition as the film is being deposited (either by thermal evaporation or by sputtering), the chemically different regions create stresses in the film and raise H(c). This periodic variation in the composition is simple to accomplish and results in a variation as a function of the thickness.

A specific example is doped EuO films. The films are prepared by the simultaneous triple evaporation of Eu, Eu(2)O(3) and the dopant. Consider Fe as the dopant. By maintaining a constant evaporation rate ratio of Eu/Eu(2)O(3) =
4.25A/sec over 4.80A/sec = 0.89 and periodically varying the Fe evaporation rate from 0 to 1/2 A/sec with a period of 50 sec for a total of 10 periods, an inhomogeneous film; as prepared with Eu + EuO and Fe k Eu k EuO regions periodically changing across the thickness of the film. H(c) was measured at 5 degrees K to be 255 Oe, in contrast to 60 Oe for films prepared under similar conditions, but with a uniform Fe evaporation rate. This is...